Early-age shrinkage behavior of cement mixtures regulated with metakaolin-based internal conditioning

Shrinkage occurs in concrete during its hardening and strength gain process leading to undesired deformation, cracking, and decreases in strength and durability. While metakaolin-based internal conditioning (MIC) has been validated as a promising technique for modifying cement and mitigating alkali-silica reactions in concrete, its impact on the early-age shrinkage behavior of cement remains unexplored. This study delves into the effects of MIC and its coupling with lithium on the chemical shrinkage, autogenous shrinkage, and drying shrinkage of portalnd cement incorporating 30 % metakaolin with varying degrees of saturation (50 %, 75 %, and 100 %). The results indicate that the hydration of cement can be substantially enhanced by MIC with 29.0 % more heat released and a 32.3 % decrease in calcium hydroxide content. As a result of the enhanced hydration, cement with MIC yielded increased chemical shrinkage. Compared with dry MK, the autogenous shrinkage and drying shrinkage of cement were decreased by 38.0 % and 11.0 %, respectively, in the presence of MIC. A synergistic effect between MIC and lithium was suggested by the higher efficacy in suppressing autogenous shrinkage.